Combined outboard motor and rudder device

ABSTRACT

The present invention relates to a combined outboard motor and rudder device, comprising:
         an upper part and a helm connected to said upper part,   two elongate rudder blades which are connected to said upper part and extend downward from said upper part in a substantially vertical direction, wherein the two rudder blades are constructed to function as a rudder,   a motor and a propeller which is rotatable about a rotation axis, wherein the rotation axis is mounted to the rudder blades via a bearing and a housing, and wherein when seen in front view the rotation axis is positioned between the rudder blades.

BACKGROUND OF THE INVENTION

The present invention relates to a combined outboard motor and rudder device. Combined outboard motor and rudder device of different kinds are known.

For the directional control and for the propulsion of small and middle sized vessels an outboard propeller is often connected to the stern or bow of the vessel. Directional control is generally only possible when the motor is running. A non-running motor generally results in an insufficient lift, in the sense that the sideways pressure on the rudder is insufficient to steer the vessel.

DISCUSSION OF THE PRIOR ART

Generally, a propeller of an outboard motor is positioned relatively close to the water surface. If the distance between the propeller and the water surface is used to provide a rudder, the rudder generally works fine at a relatively high speed. At lower speeds, the rudder tends to generate an insufficient force (or lift) to steer the vessel according to requirements.

From U.S. Pat. No. 5,102,359 an electrically driven propeller is known, which is mounted between two small vertical blades (or tailpieces), which serve as rudder. The small vertical blades extend adjacent the propeller and protrude to the rear beyond the propeller, in order to protect the propeller. A disadvantage of this outboard motor is that the vertical blades are very small, and have a great distance between them. The mounting of the outboard motor to the boat by means of a bridge-type construction is a further disadvantage. When this outboard motor is used to propel a boat, not enough lift is generated for a proper directional control.

GB2231545 discloses an outboard motor which is mounted to the underside of a single rudder blade (or tailpiece) and which has a motor and/or power supply which is mounted at the upper end near the helm. A disadvantage of this variant is that insufficient lift will be generated when the boat is sailed at a relatively low speed, because of the limited surface area of the ruder blade.

SUMMARY OF THE INVENTION

The present invention overcomes one or more of these disadvantages. To this end, the present invention provides a combined outboard motor and rudder device, comprising:

-   -   an upper part and a helm connected to said upper part,     -   two elongate rudder blades which are connected to said upper         part and extend downward from said upper part in a substantially         vertical direction, wherein the two rudder blades are         constructed to function as a rudder,     -   a motor and a propeller which is rotatable about a rotation         axis, wherein the rotation axis is mounted to the rudder blades         via a bearing and a housing, and wherein when seen in front view         the rotation axis is positioned between the rudder blades.

Generally, the rudder blades are positioned at such a distance from one another that in use a part of the water which is thrust by the propeller flows between the rudder blades and causes a Venturi effect, thereby enhancing the rudder function of the rudder blades.

The water may flow through between the rudder blades and subsequently be thrust by the propeller. It is also possible that the water is thrust by the propeller first and subsequently flows between the rudder blades.

The present invention provides a combined outboard motor and rudder device which may be used on waterborne craft such as a small boat or sailing vessel.

The two rudder blades provide a greater steering capability than a single rudder blade. Because of the Venturi effect, the steering capability is even greater.

Thus, even if only a limited water depth is provided between the propeller and the water surface, the invention provides sufficient steering capability at a relatively lower speed.

In an embodiment, the combined outboard motor and rudder device is electrically driven.

The motor may be provided in the housing or be provided above the water level and connected to the propeller via a drive shaft and one or more couplings which transmit a rotary force at a right angle or a substantially right angle.

The housing of the motor is mounted to the two elongate, substantially vertical rudder blades.

In an embodiment, the distance between the rudder blades is 50-60 percent of the length of the rudder blades. It was found that this distance provides a good Venturi effect.

Each rudder blade has a height, a width and a length. The length is the dimension of the rudder blade in the direction of travel of the vessel. The width is the maximum thickness of each rudder blade. The height is the dimension in a vertical direction.

In an embodiment, the two rudder blades extend substantially parallel to one another and are positioned at a distance from one another. A parallel configuration results in a simple form.

In an embodiment, the housing is provided at a lower end of said rudder blades. This embodiment results in a simple form

In an embodiment, the two rudder blades extend further downwards from the housing. In this way, it is relatively easy to provide a large surface area of the rudder.

The two blades are positioned at a distance from one another and define a gap. In an embodiment, the width of each rudder blade is between 8 and 12% of the length of the rudder blade. Preferably, the thickness of the blades is about 10% of the length of the blades. It was found that this ratio result in a high lift force compared to the drag force, i.e. a high L/D ratio.

Generally, the profile of the rudder blade will be according to a NACA airfoil.

In an embodiment, the housing which houses the motor is positioned centrally, when seen in front view. A central housing is a logical choice and results in a simple overall design.

In an embodiment, the propeller is positioned to the rear of a trailing edge of the rudder blades, when seen in side view. This position results in a part of the water flowing through the opening defined between the rudder blades before being thrust by the propeller. This will result in a good laminar flow between the rudder blades.

However, it is also possible that the propeller is positioned in front of the rudder blades.

In an embodiment, the diameter of the propeller is greater than the gap between the rudder blades. In this embodiment, a part of the water which is thrust by the propeller will not flow between the rudder blades, but will flow on the outer side of the rudder blades.

In an embodiment, a substantially vertical fin protrudes downward from an underside of a housing of the motor. The fin is positioned centrally. The propeller protrudes from the rear of the housing.

In an embodiment, the combined outboard motor and rudder device is pivotable about a substantially vertical pivot axis. The substantially vertical axis is located centrally between the two rudder elements, when seen in front view.

In an embodiment, the combined outboard motor and rudder device is retractable, for instance by being pivotable upwards about a horizontal pivot axis. The pivot axis is located at the height of the stern-post of the boat or at the height of the bow-post.

The housing of the motor is preferably mounted substantially between the two rudder blades. The housing of the motor projects a certain distance to the rear of said rudder blades.

In an embodiment, the combined outboard motor and rudder device is pivotable about an imaginary vertical axis, which is located between the rudder blades. In an embodiment, the rudder blades together with the housing of the motor are pivotably connected to the boat.

In the following, the aspects, features and advantages of the present invention will be elucidated further by reference to the annexed Figures illustrating exemplary embodiments. In the Figures, the same parts or parts having the same function have been identified with the same reference numeral.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows a diagrammatic orthogonal view of the combined outboard motor and rudder device according to the invention.

FIG. 2 shows a diagrammatic orthogonal view of another embodiment of the invention.

DETAILED DESCRIPTION OF THE FIGURES

FIG. 1 shows a preferred embodiment of the combined outboard motor and rudder device 1.

The combined outboard motor and rudder device 1 comprises a helm 3 which is connected to an upper part 2. Two elongate rudder blades 4 a and 4 b are connected to the upper part 2 and extend downward from the upper part 2. The rudder blades 4 may also be referred to as tailpieces or rudder elements 4. Each rudder blade 4 has a height 16, a width 18 and a length 20.

A housing 5 is connected to both rudder blades 4 a, 4 b. The housing provides a sturdy connection between the rudder blades. The provision of two rudder blades 4 a, 4 b at a distance from one another, and the upper part connecting the rudder blades near an upper end and the housing connecting the rudder blades below the water results in a stiff overall construction. The configuration is comparable to a truss beam

The combined outboard motor and rudder device 1 comprises an electric motor 10 which is provided inside a housing 5. The rudder blades 4 also have a function of a pole for providing the motor 1 at a certain depth below a water surface.

The rudder blades 4 a, 4 b have a trailing edge 14.

The combined outboard motor and rudder device 1 comprises various electronic parts (not shown) for the control of the motor 10, which are located in an upper part 2.

The combined outboard motor and rudder device 1 is retractable to a position above the water surface.

With the combined outboard motor and rudder device according to the invention, no separate rudder is required.

The rudder blades 4 a, 4 b extend parallel to one another and define a gap in between the rudder blades. The gap should be about 50-60% of the length of the rudder blades. When the rudder blades have a length of about 16 cm, the distance 8 between the rudder blades 4 a, 4 b may be about 7-11 cm. For a good Venturi effect, a distance 8 of about 8-10 cm is preferred.

For larger boats, the size of the rudder blades 4 a, 4 b may be scaled up. The distance 8 between the rudder blades will also be scaled up in a linear fashion.

When the gap 8 is too small, turbulence is created between the rudder blades 4 a, 4 b, which is detrimental to the performance.

The rudder blades 4 a, 4 b have a profile which is similar to the profile of a wing. A NACA type airfoil is generally preferred. The width is between 8 and 12% of, preferably about 10% of the length of the rudder blade element, i.e. 10% of the chord of the rudder blade. Preferably, the length of the rudder blades is about 16 cm.

Preferably the width of each rudder blade 4 a, 4 b is between 1 and 2 cm i.e. preferably about 1,5 cm.

The housing 5 is mounted at the lower end of the rudder blades 4 a, 4 b. In top view, the housing is mounted substantially between the rudder blades 4 a, 4 b. The housing 5 is mounted in such a way that a propeller 6 is positioned to the rear of the rudder blades 4.

The propeller is mounted on a rotation axis.

In the shown embodiment, a fin 9 is mounted at the underside of the housing 5 and extends downward from the housing 5. It is also possible that no fin is provided. It is also possible that the rudder blades extend further downward below the rotation axis.

The combined outboard motor and rudder device 1 comprises connection means 12 for connecting the outboard motor and rudder device 1 to a vessel. The connecting means 12 20 are schematically indicated with element 12, and are known from the prior art. Different types of connecting means are known, such as a bracket with a fastener. The combined outboard motor and rudder device may comprise a hinge for connection the hull of a vessel.

In use, the rudder blades define a constricted area of flow, resulting in an increased velocity of the water relative to the rudder blades 4 a, 4 b at the point where the thickness of the rudder blades is at its maximum.

In use, the upper part 2 is located above the water line. The rudder blades 4 a, 4 b will pierce the water line and extend partially above the water line and partially below the water line.

An advantage of this embodiment is that it is also possible to steer the boat when the motor is not running or when the boat is travelling at a low speed.

It is possible that in a second embodiment, the combined outboard motor and rudder device 1 can not be pivoted away, but is mounted in a permanent fashion to the hull of the vessel and serves as a permanent replacement of a rudder.

In this second embodiment, the two elongate rudder blades or tail pieces will still be present, and the motor housing 5 will also be mounted between the rudder blades 4 a 4 b at the lower end.

Turning to FIG. 2, another embodiment is shown, wherein the rudder blades 4 a, 4 b extend beyond the housing 10 to a greater depth than the housing. A fin 9 is not present. This embodiment has a greater surface area of the rudder blades 4 a, 4 b which results in more steering power. This embodiment is not limited by a possible shallow depth of the propeller.

It will be obvious to a person skilled in the art that the details and the arrangement of the parts may be varied over considerable range without departing from the spirit of the invention and the scope of the claims. 

1. Combined outboard motor and rudder device, comprising: an upper part and a helm connected to said upper part, two elongate rudder blades which are connected to said upper part and extend downward from said upper part in a substantially vertical direction, wherein the two rudder blades are constructed to function as a rudder, a motor and a propeller which is rotatable about a rotation axis, wherein the rotation axis is mounted to the rudder blades via a bearing and a housing, and wherein when seen in front view the rotation axis is positioned between the rudder blades.
 2. Combined outboard motor and rudder device according to claim 1, wherein the rudder blades are positioned at such a distance from one another that in use a part of the water which is thrust by the propeller flows between the rudder blades and causes a Venturi effect, thereby enhancing the rudder function of the rudder blades.
 3. Combined outboard motor and rudder device according to claim 1, characterized in that the distance between the rudder blades is 50-60 percent of the length of the rudder blades.
 4. Combined outboard motor and rudder device according to claim 1, wherein the housing is provided at a lower end of said rudder blades.
 5. Combined outboard motor and rudder device according to claim 1, characterized in that the two rudder blades extend further downwards from the housing.
 6. Combined outboard motor and rudder device according to claim 1, characterized in that the two rudder blades extend substantially parallel to one another and are positioned at a distance from one another.
 7. Combined outboard motor and rudder device according to claim 1, characterized in that the width of each rudder blade is between 8 and 12% of the length of the rudder blade.
 8. Combined outboard motor and rudder device according to claim 1, characterized in that the housing which houses the motor is positioned centrally, when seen in front view.
 9. Combined outboard motor and rudder device according to claim 1, characterized in that the propeller is positioned to the rear of a trailing edge of the rudder blades, when seen in side view.
 10. Combined outboard motor and rudder device according to claim 1, characterized in that the propeller is positioned to the front of a front edge of the rudder blades, when seen in side view.
 11. Combined outboard motor and rudder device according to claim 1, characterized in that the combined outboard motor and rudder device is pivotable about a vertical axis which is located between the rudder blades, when seen in front view.
 12. Combined outboard motor and rudder device according to claim 1, characterized in that the combined outboard motor and rudder device is movable between a working position and a retracted position.
 13. Combined outboard motor and rudder device according to claim 1, characterized in that the combined outboard motor and rudder device comprises a hinge which defines a substantially horizontal pivot axis, wherein the hinge is configured to be connected to a hull of a vessel.
 14. Combined outboard motor and rudder device according to claim 1, wherein the upper part accommodates an electronic control device for controlling the motor. 